1. FIELD OF THE INVENTION
The present invention relates to an elevator control device. More particularly, it relates to an elevator control device which corrects deviations at the stop position attributable to variations in the stretching of a cable. These variations are caused by factors, such as a change in the load acting on a car when passengers get in and out of an elevator.
2. DESCRIPTION OF THE RELATED ART
Generally, elevators require precise level control functions. A leveling control controls the a stop position of an elevator so that the difference in the levels of the floor of the car at rest and a hall floor can be minimized as much as possible.
In elevators at high floors, the load acting on the car while the elevator is at rest may vary because passengers get in and out, or goods are loaded and unloaded. This variation causes a change in the stretching of a suspending cable. The level of the car may deviate considerably.
In such an elevator, the stretch of the rope has hitherto been compensated, and the leveling control mentioned above is performed. The leveling control is performed at a slow speed while the door is opened for passengers to get in and out of the car so that they do not feel uneasy. The compensation for the stretching of the cable, together with the leveling control, is hereinafter referred to as a readjusting control.
Because the readjusting control is performed while the door is open, it is stopped once a control for closing the door is performed. The completion of the operation of a door timer is one of the conditions under which the door is closed. The door timer sets the amount of time during which the door is open. When such a condition is met, a door-open command is made inoperable, thus causing the door to begin closing.
Therefore, even while the readjusting control is ongoing, if the operation of the above door timer is completed, making the door-open command inoperable, the readjusting control is terminated. The car stops before it reaches the level of the hall floor, with the result that the difference in the levels of the hall floor and the elevator may not be corrected.
Since the readjusting control is stopped, vibrations occur when the car is at rest, thereby making the passengers feel uneasy.
To cope with such a problem, Japanese Patent Laid-Open No. 1-288583 discloses a device provided with a means to retain a door-open command, thereby permitting the continuation of the readjusting control, even when the elevator enters into a mode in which the completion of the door timer makes the door-open command inoperable. In the above device, the level of the car deviates because passengers get in and out, or goods are loaded and unloaded. Therefore, during the readjusting control, even after the operation of the door timer has been completed and the elevator enters into a mode for closing the door, the readjusting control is performed until the level of the elevator reaches a predetermined value. However, when the door must be closed, closing of the door may be delayed during the readjusting control. This is a problem because it decreases the operational efficiency.